Anybody know of a source that can custom make SU needles?
After much filing and testing, I've cured the lean cruise problem I've
been having. What a difference a .001" makes at the right point :)
I'd like to establish the profile I now have as a baseline for further
enrichening, but I don't want to have to refile stock needles every
time. I've used the "needles" program to search for a similar profile,
but nothing comes close.
For the curious:
1970 MGB
HS4, newly rebushed and rebuilt
Bored +.040"
Kent Mild street cam
Head Porting per Burgess
1.625 inlet valves
Stock Air Cleaners
Exhaust mfg. unknown, (non-stock)
Basically, I started with an ABD needle and determined the locations of
the 16 stations using a 1/64" Steel rule and a Mitutoyo digital caliper.
I made a measurement jig out of 1/8" flat steel with the rule taped to
it. This allowed me to lay the shoulder of the needle against the edge
and mark off the station locations. I started at station 3 and reduced
the taper by ~.001 with a small flat file followed by 220 grit and then
600 grit to finely polish the needle. All told it took about 3 hours to
match the needles to each other.
Made all the difference in the world. I was experiencing a definite
"lean cruise" condition, sort of a surging or "wind against the car"
feeling around 40 mph in 4th with light throttle. Plugs were bone white
when pulled. Now the "surge" is gone, plugs showing light tan and the
exhaust has a definite stronger note to it. Completely different car now
:)
Jeff
'70MGB
BTW: The "needles" program is great, has anybody made a Windows version
of it? If not I may have to and donate it...
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